This invention relates generally to vehicle occupant passive restraint systems and, more particularly, to improved arrangements and methods for attaching airbag cushions such as used in such systems.
It is well known to protect a vehicle occupant by means of an inflatable vehicle occupant restraint, such as in the form of a cushion or bag, commonly referred to as an "airbag cushion." In practice, it is common that inflatable vehicle occupant restraints be designed to inflate into a location within the vehicle between the occupant and certain parts of the vehicle interior, such as the doors, steering wheel, instrument panel or the like, to prevent or avoid the occupant from forcibly striking such parts of the vehicle interior. In practice, such airbag cushions are typically inflated or expanded with gas when the vehicle encounters sudden deceleration, such as in the event of a collision.
In such systems, airbag cushions are normally housed in an uninflated and folded condition to minimize space requirements. Such systems also typically include one or more crash sensors mounted on or to the frame or body of the vehicle to detect sudden decelerations of the vehicle and to electronically trigger activation of the system. Upon actuation of the system, such as upon receipt of an appropriate signal from the associated system crash sensor, the cushion begins to be inflated, in a matter of no more than a few milliseconds, with gas produced or supplied by a device commonly referred to as an "inflator."
Airbag module assemblies typically involve the manufacture, installation and inspection of many and various component parts. Common airbag module assembly components typically include a cover, an airbag cushion, a means for holding the airbag cushion such as an annular retainer or retaining ring, a supporting plate such as a module housing or mounting plate, a gas generator or inflator, fasteners and means to attach the assembly to a steering wheel, dashboard or other appropriate vehicle structure.
It is common that in such airbag module assemblies, the airbag cushion include a relatively large and generally centrally located inflation gas inlet opening, which is held or otherwise clamped between a flange of the inflator, such as extending circumferentially about a disk-shaped inflator device, and an annular retaining ring through a module housing or mounting plate. Rivets or other form of fasteners are typically used to attach the retaining ring to the gas inlet opening of the airbag cushion at various attachment points spaced about the periphery of the inflator. The retaining ring, with the airbag cushion affixed thereto, is then bolted to the module housing and the flange of the inflator with the inflator so arranged that the flange thereof is positioned externally of the airbag cushion and the module housing.
As will be appreciated, in order to permit the inflation of an airbag cushion within the relatively short available time period, gas or other inflation medium is generally expelled or discharged from an associated inflator at a relatively high flow rate or velocity. Such high flow rate or velocity discharges can create forces within the airbag cushion such as may tend to blow or otherwise force the airbag cushion from the inflator.
In such assemblies, the force holding the airbag cushion to the inflator and the module housing may concentrate to form undesirable shearing stresses on the assembly and in particular on the airbag cushion such at one or more of the fastening sites. In view thereof, airbag cushions are commonly fabricated to include several reinforcement layers in the vicinity of the central inflation gas inlet opening whereat the airbag cushion is held or otherwise clamped. While the inclusion of such reinforcement layers may help the airbag cushion to structurally withstand such deployment stresses, the inclusion of such reinforcements almost invariably increases the cost of either or both manufacture and assembly.
Further, the use of multiple rivets, bolts or other, similar, fastening means to attach an airbag cushion to an associated retainer ring or other module component can be a cause for reworking inflator module assemblies in the manufacture thereof. When reworking is not possible, defective airbag modules must be discarded.
In addition, while a strong form of joinder, attachment or mounting of an airbag cushion with an associated inflator or airbag module structure is generally desired to better assure retention of the airbag cushion upon deployment thereof, it is also generally desirable that the form of joinder, attachment or mounting be simple to assemble and inexpensive to produce.
Still further, the inclusion of a flange, such as extending circumferentially about a disk-shaped inflator device, may undesirably increase assembly weight.
Thus, there is a need and a demand for the provision of improved arrangements and methods for attaching airbag cushions used in vehicle occupant passive restraint systems.
In particular, there is a need and a demand for arrangements and methods for attaching airbag cushions used in vehicle occupant passive restraint systems which minimize or avoid the problems and associated failure possibilities which may exist or be associated with module assemblies which rely on the use of multiple rivets, bolts or other, similar, fastening means to attach an airbag cushion to an associated retainer ring or other module component and which may further reduce or minimize the costs associated with either or both the manufacture and assembly thereof.